Infusion system using optical imager for controlling flow and method thereof

ABSTRACT

A method of operating an infusion pump includes transmitting light through or around a drop of fluid suspended from an end of a drip tube for the infusion pump, the end of the drip tube located in a drip chamber for the infusion pump, wherein the drip tube is configured for connection to a source of the fluid; receiving, using an optical system for the pump, light transmitted through or around the drop; transmitting, to a specially programmed microprocessor and using the optical system, data regarding the received light; and, using the microprocessor to calculate a volume of the drop using the data.

RELATED APPLICATION

This application is a continuation of, and claims 35 U.S.C. § 120priority from, U.S. patent application Ser. No. 15,462,188, filed Mar.17, 2017, which is a continuation of U.S. patent application Ser. No.14/086,561, filed Nov. 21, 2013, now U.S. Pat. No. 9,603,999, which is acontinuation of U.S. patent application Ser. No. 12/907,403, filed Oct.19, 2010, now U.S. Pat. No. 8,622,979.

BACKGROUND

The present disclosure relates generally to a pump with optical imagingfor calculating drop size and flow rate and for use in pump control andalarm operations.

Prior art references, such as U.S. Pat. No. 4,936,828 (Chiang, Kophu),U.S. Pat. No. 5,588,963 (Roelofs; Bernardus J. G. M.), and U.S. Pat. No.6,213,354 (Kay, Robert L.) teach respective infusion systems which useoptical systems to measure the volume of falling drops. That is, theprinciple of operation set forth in the prior art, and in the precedingreferences in particular, is necessarily connected to operations upon adrop that is in free fall through a drip chamber.

SUMMARY

The invention broadly comprises an infusion pump, including: a firstspecially programmed microprocessor; a drip chamber for connection to anoutput tube; a drip tube for connection to a source of fluid and with anend disposed in the drip chamber; and an illumination system: with alight source for transmitting light through a wall of the drip chamberto a drop of fluid suspended from the end of the drip tube; and forcontrolling illumination properties of the light transmitted to thedrop. The pump also includes an optical system for: receiving lighttransmitted through the drop; and transmitting, to the firstmicroprocessor, data regarding the received light. The firstmicroprocessor is for: generating, using the data, an image of the drop;locating, using the image, an outer edge of the drop to define aboundary of the drop; integrating an area enclosed by the boundary; andcalculating a volume of revolution for the drop with respect to an axisfor the drop that intersects the end of the drip tube, assuming symmetryof the drop with respect to the axis.

The invention broadly comprises an infusion pump, including: a speciallyprogrammed microprocessor; a drip chamber for connection to an outputtube; a drip tube for connecting the drip chamber to a source of fluid,the drip tube including an end disposed within the drip chamber; anillumination system including a lighting element for transmitting lightthrough or around a drop of fluid hanging from the end of the drip tube;and an optical system for receiving light transmitted through or aroundthe drop and transmitting, to the microprocessor, data regarding thereceived light. The illumination system includes one of a telecentriclighting element, a structured lighting element, a pair of laser lightsources disposed at an acute angle with respect to each other and forgenerating respective light beams that interact to form an interferencepattern, or a projection lens with a pattern in or on a surface of thelens and through which the lighting element transmits light to projectthe pattern onto the drop. The telecentric lighting element includes atelecentric lens and a first light source and the telecentric lensbundles light rays from the first light source and directs the bundledlight rays toward the drop. The structured lighting element includes asecond light source and a structural element placed between the secondlight source and the drop to block or alter light emanating from thesecond light source. The microprocessor is for calculating a volume ofthe drop using the data.

The invention broadly comprises an infusion pump, including: a speciallyprogrammed microprocessor; a drip chamber for connection to an outputtube; a drip tube for connecting the drip chamber to a source of fluid,the drip tube including an end disposed within the drip chamber; and anillumination system, including a light source for transmitting lightinto the drip tube such that: the light reflects off a plurality ofportions of an internally facing surface of the drip tube; and thereflected light is transmitted through the end of the drip tube into aninterior of a drop of the fluid hanging from the end of the drip tubesuch that the interior of the drop is uniformly illuminated. The pumpalso includes an optical system for receiving light transmitted from theinterior of the drop and transmitting, to the microprocessor, dataregarding the received light. The microprocessor is for calculating, avolume of the drop using the data.

The invention broadly comprises an infusion pump, including: a speciallyprogrammed microprocessor; a drip chamber for connection to a source offluid and an output tube; and an illumination system including a lightsource for transmitting light, at an acute angle with respect to alongitudinal axis for the drip chamber, into the drip chamber such thatthe light reflects, at the acute angle, off a surface of the fluidpooled within the drip chamber. The pump also includes an optical systemfor receiving light reflected off the surface and transmitting, to themicroprocessor, data regarding the received light. The microprocessor isfor calculating a position of the surface using the data regarding thereceived light.

The invention broadly comprises an infusion pump, including: anillumination system; an optical system; and a specially programmedmicroprocessor. The illumination system is for: illuminating an end of adrip tube located within a drip chamber of the infusion pump, the driptube for connecting the drip chamber to a source of fluid; andilluminating a drop of the fluid hanging from the end of the drip tube.The optical system is for: receiving first light emanating from the endof the drip tube and second light emanating from the drop andtransmitting data regarding the received light to the microprocessor.The microprocessor is for: generating respective images of the drop andthe end of the drip tube from the data; locating an apex of the dropfrom the image, the apex being a portion of the drop at a furthestdistance from the end of the drip tube; determining, using the locationof the apex, an orientation of the drop with respect to the end of thedrip tube; and calculating, using the orientation of the drop withrespect to the end of the drip tube, an orientation of the drip chamber.

The invention broadly comprises an infusion pump, including: a speciallyprogrammed microprocessor; a drip chamber for connection to an outputtube; a drip tube for connecting the drip chamber to a source of fluid,the drip tube including an end disposed within the drip chamber; and anillumination system: including a light source for transmitting lightthrough the wall of the drip chamber to a drop of fluid suspended fromthe first end of the drip tube; and for controlling the illuminationproperties of the light transmitted to the drop. The pump also includesan optical system for: receiving light transmitted through the drop; andtransmitting data regarding the received light to the microprocessor.The microprocessor is for: generating respective images of the drop andthe end of the drip tube from the data; calculating, using therespective images, a boundary of the end of the drip tube; and using theboundary as a reference plane for calculating a volume, shape, orlocation of the drop.

The invention broadly comprises an infusion pump, including: amicroprocessor; a drip chamber for connection to an output tube; a driptube for connection to a source of fluid and with an end disposed in thedrip chamber; and an illumination system: including a light source fortransmitting light through the wall of the drip chamber to the end ofthe drip tube or proximate the end of the drip tube; and for controllingthe illumination properties of the transmitted light. The pump alsoincludes an optical system for: receiving light transmitted through theend of the drip tube or proximate the end of the drip tube; andtransmitting, to the microprocessor, data regarding the received light.The microprocessor is for: generating an image of the end of the driptube from the data; determining that a drop of the fluid is absent fromthe end of the drip tube for a specified period of time; and generatingan empty bag alarm or an air-in-line alarm.

The invention broadly comprises an infusion pump, including: a speciallyprogrammed microprocessor; a drip chamber for connection to an outputtube; a drip tube for connection to a source of fluid and with an enddisposed in the drip chamber; and an illumination system: including alight source for transmitting light through the wall of the drip chamberto a drop of fluid suspended from the first end of the drip tube; andfor controlling the illumination properties of the transmitted light.The pump also includes an optical imaging system for: receiving lighttransmitted through the drop; and transmitting, to the microprocessor,data regarding the received light. The microprocessor is for: creating aplurality of temporally successive images of the drop from the data;calculating a respective volume for the drop in each successive image;identifying changes in the respective volumes; and calculating a flowrate of fluid to the output tube based on the changes in the respectivevolumes.

The invention broadly comprises an infusion pump, including: a speciallyprogrammed microprocessor; a drip chamber for connection to an outputtube; a drip tube for connection to a source of fluid and with an enddisposed in the drip chamber; and an illumination system: including alight source for transmitting light through a wall of the drip chamberto a drop of fluid suspended from the end of the drip tube; and forcontrolling the illumination properties of the transmitted light. Thepump also includes an optical imaging system for: receiving lighttransmitted through the drop; and transmitting, to the microprocessor,data regarding the received light; and a pumping mechanism acting on theoutput tube to displace fluid from the drip chamber through the outputtube. The microprocessor is for: creating a plurality of temporallysuccessive images of the drop from the data; calculating a respectivesize for the drop in each successive image; identifying changes in therespective sizes; calculating a flow rate of fluid to the output tubebased on the changes in the respective sizes; and controlling thepumping mechanism to match the flow rate of fluid with a desired flowrate of fluid.

The invention broadly comprises a dual infusion pump configuration,including: a specially programmed microprocessor; first and second dripchambers for connection to first and second output tubes, respectively;first and second drip tubes for connection to first and second sourcesof fluids, respectively, and with first and second ends disposed in thefirst and second drip chambers, respectively; and first and secondillumination systems: including first and second light source fortransmitting first and second light through walls of the first andsecond drip chambers, respectively, to drops of the first and secondfluids, suspended from the first and second ends of the first and seconddrip tubes, respectively; and for controlling first and secondillumination properties of the first and second light transmitted to thedrops of the first and second fluids, respectively. The configurationalso includes: first and second optical systems for: receiving first andsecond light transmitted through the drops of the first and secondfluids, respectively; and transmitting, to the microprocessor, first andsecond data regarding the first and second received light; and first andsecond pumping mechanisms for acting on the first and second outputtubes to displace first and second fluid from the first and second dripchambers through the first and second output tubes, respectively. Themicroprocessor is for: operating the first pumping mechanism to generatea first flow rate for the first fluid from the first drip chamberthrough the first output tube; creating, from the first data, aplurality of temporally successive images of the drop of the firstfluid; determining, using the first plurality of temporally successiveimages, that the first source of fluid is empty when the drop of thefirst fluid is absent from the first end of the first drip tube for aspecified period of time; and operating the second pumping mechanism togenerate a second flow rate for the second source of fluid from thesecond drip chamber through the second output tube in response todetermining that the first source of fluid is empty.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light through a wall of a drip chamber for theinfusion pump to a drop of fluid suspended from an end of a drip tubefor the infusion pump, the drip tube being for connection to a source offluid and the end of the drip tube being disposed in the drip chamber;controlling, using an illumination system for the infusion pump,illumination properties of the light transmitted to the drop; receiving,using an optical system for the pump, light transmitted through thedrop; detecting, using the optical system, an image; transmitting, to afirst specially programmed microprocessor and using the optical system,data regarding the image; and using the first microprocessor to: locate,from the data, an outer edge of the drop to define a boundary of thedrop; integrate an area enclosed by the boundary; and calculate a volumeof revolution for the drop with respect to an axis for the drop thatintersects the end of the drip tube, assuming symmetry of the drop withrespect to the axis.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light through or around a drop of fluidsuspended from an end of a drip tube for the infusion pump, the end ofthe drip tube located in a drip chamber for the infusion pump, the driptube being for connection to a source of the fluid; receiving, using anoptical system for the pump, light transmitted through or around thedrop; transmitting, to a specially programmed microprocessor and usingthe optical system, data regarding the received light; and using themicroprocessor to calculate a volume of the drop using the data.Transmitting light includes: using a telecentric lighting elementincluding a telecentric lens and a first light source, the telecentriclens bundling light rays from the first light source and directing thebundled light rays toward the drop; using a structured lighting elementincluding a second light source and a structural element placed betweenthe second light source and the drop to block or alter light emanatingfrom the second light source; using a pair of laser light sourcesdisposed at an acute angle with respect to each other to generaterespective light beams that interact to form an interference pattern; ortransmitting light through a projection lens, the lens having a patternin or on a surface of the lens, to project the pattern onto the drop.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light into a drip tube for the infusion pump, anend of the drip tube disposed in a drip chamber for the infusion pumpsuch that: the light reflects off a plurality of portions of aninternally facing surface of the drip tube; and the reflected light istransmitted through the end of the drip tube into an interior of a dropof fluid hanging from the end of the drip tube such that the interior ofthe drop is uniformly illuminated, wherein the drip tube is forconnection to a source of the fluid. The method also includes:receiving, using an optical system for the pump, light transmitted fromthe interior of the drop; transmitting, to a specially programmedmicroprocessor and using the optical system, data regarding the receivedlight; and calculating, using the microprocessor, a volume of the dropusing the data.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light, at an acute angle with respect to alongitudinal axis for a drip chamber for the infusion pump, into thedrip chamber such that the light reflects, at the acute angle, off asurface of fluid pooled within the drip chamber; receiving, using anoptical system for the pump, light reflected from the surface;transmitting, to a specially programmed microprocessor and using theoptical system, data regarding the received light; and calculating,using the processor, a position of the surface using the data regardingthe received light.

The invention broadly comprises a method for operating an infusion pump,including: illuminating, using an illumination system for the infusionpump, an end of a drip tube located within a drip chamber of theinfusion pump, the drip tube for connecting the drip chamber to a sourceof fluid; illuminating, using the illumination system, a drop of thefluid hanging from the end of the drip tube; and using an optical systemto: receive first light emanating from the end of the drip tube andsecond light emanating from the drop; and transmit data regarding thereceived first and second light to a specially programmedmicroprocessor. The method also includes using the microprocessor to:generate respective images of the end of the drip tube and the drop fromthe data; locate an apex of the drop, the apex being a portion of thedrop at a furthest distance from the end of the drip tube; determine,using the location of the apex, an orientation of the drop with respectto the end of the drip tube; and calculate, using the orientation of thedrop with respect to the end of the drip tube, an orientation of thedrip chamber.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light through a wall of a drip chamber for theinfusion pump to a drop of fluid suspended from an end of a drip tubefor the infusion pump, the drip tube being for connection to a source offluid and the end of the drip tube being disposed in the drip chamber;controlling, using an illumination system for the infusion pump,illumination properties of the light transmitted to the drop; and usingan optical system for the pump to: receive light transmitted through thedrop; and transmit to a specially programmed microprocessor, dataregarding the received light. The method also includes using themicroprocessor to: generate, from the data, respective images of thedrop and of the end of the drip tube; calculate, using the respectiveimages, a boundary of the end of the drip tube; and calculate a volume,shape, or location of the drop using the boundary as a reference plane.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light through a wall of a drip chamber for theinfusion pump to an end of a drip tube or proximate the end of the driptube, the drip tube being for connection to a source of fluid and theend of the drip tube being disposed in the drip chamber; controlling,using an illumination system for the infusion pump, illuminationproperties of the transmitted light transmitted to the drop; and usingan optical system for the pump to: receive light transmitted through theend of the drip tube or proximate the end of the drip tube; andtransmit, to a specially programmed microprocessor, data regarding thereceived light. The method also includes: using the microprocessor to:generate an image of the end of the drip tube from the data; determine,from the image, that a drop is absent from the end of the drip tube fora specified period of time; and generate an empty bag alarm or anair-in-line alarm.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light through a wall of a drip chamber for theinfusion pump to a drop of fluid suspended from an end of a drip tubefor the infusion pump, the drip tube being for connection to a source offluid and the end of the drip tube being disposed in the drip chamber;controlling, using an illumination system for the infusion pump,illumination properties of the light transmitted to the drop; and usingan optical system for the pump to: receive light transmitted through thedrop; and transmit, to a specially programmed microprocessor, dataregarding the received light. The method also includes using themicroprocessor to: create a plurality of temporally successive images ofthe drop from the data; calculate a respective volume for the drop ineach successive image; identify changes in the respective volumes; andcalculate a flow rate of fluid to the output tube based on the changesin the respective volumes.

The invention broadly comprises a method for operating an infusion pump,including: transmitting light through a wall of a drip chamber for theinfusion pump to a drop of fluid suspended from an end of a drip tubefor the infusion pump, the drip tube being for connection to a source offluid and the end of the drip tube being disposed in the drip chamber;controlling, using an illumination system for the infusion pump,illumination properties of the light transmitted to the drop; and usingan optical system for the pump to: receive light transmitted through thedrop; and transmit, to a specially programmed microprocessor, dataregarding the received light. The method also includes: displacing fluidfrom the drip chamber through the output tube by operating a pumpingmechanism for the infusion pump acting on the output tube; and using themicroprocessor to: create a plurality of temporally successive images ofthe drop from the data; calculate a respective volume for the drop ineach successive image; identify changes in the respective volumes;calculate a flow rate of fluid to the output tube based on the changesin the respective volumes; and control the pumping mechanism to matchthe flow rate of fluid with a desired flow rate of fluid.

The invention broadly comprises a method of operating a dual infusionpump configuration, the configuration including a specially programmedmicroprocessor; first and second drip chambers connected to first andsecond output tubes, respectively; first and second drip tubes connectedto first and second sources of fluids, respectively, and with first andsecond ends disposed in the first and second drip chambers,respectively; first and second illumination systems; and first andsecond optical systems, including: transmitting first and second lightthrough walls of the first and second drip chambers to drops of thefirst and second fluids, suspended from the first and second ends of thefirst and second drip tubes, respectively; controlling, using the firstand second illumination systems, first and second illuminationproperties of the first and second light transmitted to the drops of thefirst and second fluids, respectively; receiving, using the first andsecond optical systems, first and second light transmitted through thedrop of the first and second fluids, respectively; transmitting, to themicroprocessor and using the first and second optical systems, first andsecond data regarding the first and second received light; acting on thefirst and second output tubes, using the first and second pumpingmechanisms, to displace first and second fluid from the first and seconddrip chambers through the first and second output tubes, respectively;and using the microprocessor to: operate the first pumping mechanism togenerate a first flow rate for the first source of fluid from the firstdrip chamber through the first output tube; create, from the first data,a plurality of temporally successive images of the drop of the firstfluid; determine, using the plurality of temporally successive images,that the first source of fluid is empty when the drop of the first fluidis absent from the first end of the first drip tube for a specifiedperiod of time; and operate the second pumping mechanism to generate asecond flow rate for the second source of fluid from the second dripchamber through the second output tube in response to determining thatthe first source of fluid is empty.

The invention broadly comprises a flow meter apparatus including: a dripchamber including an optically clear wall configured to connect to anoutput tube; a drip tube having a first end connected to a source offluid and a second end disposed in the drip chamber, the second endconfigured to position a drop of fluid from the source of fluid withinthe drip chamber; an illumination system including a light sourceconfigured to transmit light through the wall of the drip chamber, apattern configured such that the pattern, when illuminated by theillumination system, is viewable in relation to the drop of fluid; anoptical system having a sensor configured to receive light transmittedthrough the drip chamber, wherein the transmitted light provides patterndata regarding distortions in the pattern; and at least onemicroprocessor configured to: receive pattern data from the sensor; andcalculate a volume of the drop of fluid from the one or more imagesbased on distortions of the pattern in relation to the drop of fluid.

The invention broadly comprises a flow meter apparatus including: a dripchamber including an optically clear wall configured to connect to anoutput tube; a drip tube having a first end connected to a source offluid and a second end disposed in the drip chamber, the second endconfigured to position a drop of fluid from the source of fluid withinthe drip chamber; an illumination system including a light sourceconfigured to project a pattern such that the pattern is viewable on thesurface of the drop of fluid; an optical system having a sensorconfigured to receive light transmitted through the drip chamber,receive pattern data regarding the pattern on the surface of the drop,and transmit pattern data related to the received light; and at leastone microprocessor, wherein the microprocessor is configured to receivethe pattern data from the sensor, generate one or more images of thedrop of fluid, and calculate a volume of the drop of fluid from the oneor more images based on distortions of the pattern on the drop of fluid.

The invention broadly comprises a flow meter apparatus including: a dripchamber including an optically clear wall configured to connect to anoutput tube; a drip tube having a first end connected to a source offluid and a second end disposed in the drip chamber, the second endconfigured to position a drop of fluid from the source of fluid withinthe drip chamber; an illumination system including a light source totransmit light through the wall of the drip chamber; a patternconfigured such that the pattern is viewable in relation to the drop offluid; an optical system having a sensor configured to receive lighttransmitted through the drip chamber, wherein the transmitted lightprovides pattern data related to the pattern in relation to the drop offluid; and at least one microprocessor, wherein the microprocessor isconfigured to receive pattern data from the sensor, generate one or moreimages of the drop of fluid, and calculate at least one fluid propertybased on a distortion of the pattern.

The invention broadly comprises a method for operating a flow meterincluding: transmitting light through or around a drop of fluid in adrip chamber; positioning a pattern viewable in relation to the drop offluid; receiving, using an optical system having a sensor, lighttransmitted through or around the drop of fluid, wherein the lighttransmitted provides pattern data regarding the pattern; transmitting,to one or more microprocessors, pattern data from the sensor;generating, using the one or more microprocessors, one or more images ofa drop of fluid and the drip chamber; and calculating, using the one ormore microprocessors, a volume of the drop of fluid from the one or moreimages.

The invention broadly comprises a method of operating a flow meterincluding: using a pattern in association with a drip chamber, whereinthe pattern includes pattern information; generating one or more imagesof a drop of fluid and drip chamber, wherein the image is generatedusing data received from an optical system having a sensor; comparingthe one or more images of the drop of fluid with the patterninformation; and calculating at least one fluid property based on theone or more images of the drop of fluid and the pattern information.

The invention broadly comprises a method of controlling a flow meterincluding: generating one or more images of a drop of fluid and a dripchamber, wherein the image is generated using data received from anoptical system having a sensor; calculating a flow rate of fluid, usingone or more microprocessors, through the drip chamber based on datareceived from the sensor; and controlling a mechanism, using the one ormore microprocessors, to achieve a target flow rate, the mechanismincluding a flexible tube section, a pump, and one or more flowrestrictors.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature and mode of operation of the present invention will now bemore fully described in the following detailed description of theinvention taken with the accompanying drawing figures, in which:

FIG. 1 is a schematic representation of definitions for an infusionpump;

FIG. 2 is a schematic block representation of an infusion pump with anoptical imaging system;

FIGS. 3A through 3F illustrate example embodiments of the illuminationsystem shown in FIG. 2;

FIGS. 4A through 4C are schematic representation of embodiments for anoptical system;

FIGS. 5A through 5C illustrate imaging processing definitions;

FIG. 6 illustrates an image of a drop including a circle at least partlyincluded within an outer boundary of the drop

FIG. 7 is a flow chart illustrating operation of a pump with an opticalimaging system;

FIGS. 8A and 8B are schematic details for a pump implementing anoperation for determining a gravity vector;

FIGS. 9A and 9B are schematic details of a pump using light injection;

FIGS. 10A and 10B are schematic details of a pump with a meniscusdetection arrangement;

FIG. 11 is a schematic block representation of two infusion pumps withrespective optical imaging system in a primary and secondaryconfiguration;

FIG. 12 is a top-level block diagram illustrating operation of a pumpwith an optical imaging system;

FIG. 13 is a block diagram illustrating example signal processing andfeedback control for a pump with an optical imaging system;

FIG. 14 is a block diagram illustrating example digital filtering in apump with an optical imaging system; and,

FIG. 15 is a schematic representation of example spatial filtering in apump with an optical imaging system.

DETAILED DESCRIPTION

At the outset, it should be appreciated that like drawing numbers ondifferent drawing views identify identical, or functionally similar,structural elements of the invention. While the present invention isdescribed with respect to what is presently considered to be thepreferred aspects, it is to be understood that the invention as claimedis not limited to the disclosed aspects.

Furthermore, it is understood that this invention is not limited to theparticular methodology, materials and modifications described and assuch may, of course, vary. It is also understood that the terminologyused herein is for the purpose of describing particular aspects only,and is not intended to limit the scope of the present invention, whichis limited only by the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this invention belongs. Although any methods, devicesor materials similar or equivalent to those described herein can be usedin the practice or testing of the invention, the preferred methods,devices, and materials are now described.

FIG. 1 is a schematic representation of definitions for an infusionpump.

FIG. 2 is a schematic block representation of infusion pump 100 withoptical imaging system 102. Pump 100 includes specially programmedmicroprocessor 104, drip chamber 106 for connection to output tube 108,and drip tube 110 for connecting the drip chamber to a source of fluid112, for example, an IV bag. The drip tube includes end 114 disposedwithin the drip chamber. The imaging system includes illumination system118 and optical system 120. System 118 includes lighting element 122 fortransmitting light through wall 123 of the drip chamber to or arounddrop 124 of the fluid suspended from the end of the drip tube, forexample, one or both of the drip and end 114 are illuminated. System 118also controls illumination properties of the light transmitted to thedrop. System 120 receives, for example using optical sensor 126, lighttransmitted through the drop, or through or around end 114 andtransmits, to the microprocessor, data 129 regarding the received light.Pump 100 also includes pumping mechanism 127. In one embodiment, themechanism includes top and bottom flow restrictors and uses peristalticactuators, such as rollers, to displace fluid through tube 108.

FIGS. 3A through 3F illustrate example embodiments of system 118 in FIG.2. As shown in FIG. 3A, light rays 128 from a collimated illuminationsystem are parallel. As shown in FIG. 3B, light rays 130 from a diffuseillumination system are emitted in a cone-shaped pattern from each lightemitting point on an illumination plane. As shown in FIG. 3C, light rays132 from illumination source 122 pass through telecentric lens 134 andare formed into ray bundles 136. The rays in bundles 136 are very nearlyparallel. The ray bundles provide sharp definition of image edges andminimize depth distortion As shown in FIG. 3D, a structured lightingelement shapes illumination, for example, rays 138, so as to controlunwanted or stray light and to accentuate edges of an objecting beingilluminated. A structured lighting element can include barrier 139,disposed between an illumination source and an object being illuminated,for example, drop 124, to shape the illumination, for example, byblocking or altering light emanating from the source.

FIG. 3E illustrates the use of laser interference to project stripepatterns measure drop 124. Illumination source 122 includes laser lightsources 187. Sources 187 project light patterns consisting of manystripes at once, or of arbitrary fringes. This technique enables theacquisition of a multitude of samples regarding an image of drop 124,simultaneously. As seen from different viewpoints, the projected patternappears geometrically distorted due to the surface shape of the object.In one embodiment, patterns of parallel stripes are used; however, itshould be understood that other patterns can be used. The displacementof the stripes allows for an exact retrieval of the three dimensional(3D) coordinates of details on an object's surface, for example, thesurface of drop 124. Laser interference works with two wide planarfronts 189 from laser beams 191. The interference of the fronts resultsin regular, equidistant line, or interference, patterns 193. Differentpattern sizes can be obtained by changing the angle between the beams.The method allows for the exact and easy generation of very finepatterns with unlimited depth of field. FIG. 3E is a top view of pump100 and sources 187 are shown disposed radially about axis 195 for droptube 110. However, it should be understood that other configurations ofsources 187 with respect to the pump are possible, for example, parallelto axis 195.

FIG. 3F illustrates the use of projection lens 196 in system 118. InFIG. 3F, system 118 illumination source transmits light 197 through lens196. Surface 198 of the lens is modified as known in the art, forexample, etched or through deposition of chrome or other materials, toproduce a pattern on the surface. Light 197 passing through the lensprojects an image of the pattern on and about drop 124. In oneembodiment, projected pattern 199 is in the form of a constant-intervalbar and space square wave, such as a Ronchi Ruling, or Ronchi grating.

The illumination source for a structured lighting element can becollimated, diffuse, or telecentric. Structured illumination can controlunwanted or stray light and accentuate image edges. In one embodiment,the illumination system includes a telecentric lighting element. In oneembodiment, the illumination system includes a structured lightingelement.

Returning to FIG. 2, microprocessor 104 includes data processing segment140 and data acquisition and control segment 142. The pump also includescontrol panel 144, for example, any graphical user interface known inthe art. Output from the optical system, for example, data 129 fromsensor 126, is inputted to segment 142. Panel 144, or other operatorinput, is used to input a desired flow rate through the drip chamber, aswell as other necessary data such as drug type and treatmentinformation. Microprocessor 104 can be any microprocessor known in theart.

Pump 100 uses optical sensing of pendant drops, that is drops hangingfrom or suspended from end 114, to measure fluid flow through the dripchamber to the output tube and to provide input to a closed-loop pumpcontrol process controlled by the microprocessor. Fluid from source 112flows through drip tube to end 114 of the drip tube. The fluid formsdrop 124 at end 114 and when conditions in the drip tube, discussedinfra, are suitable, the drop falls from end 114 into fluid 146 in thedrip chamber. In general, a pendant drop increases in size in proportionto the outflow of fluid 146 from the drip chamber through tube 108. Thatis, an increase in the volume of the pendant drop during a time frame isequal to the volume of fluid passing from the drip chamber to tube 108in the time period. The preceding relationship is based on the followingassumptions: the fluid from the source is not compressible; source 112,the drip tube, the drip chamber, tube 108, and a patient to whom tube108 is connected are closed to outside atmosphere. Each measurement ofthe drop volume is processed to provide a fluid volume (or mass)measurement. Successive measurements of drop volume over known intervalsof time are used by the microprocessor to calculate the flow rate offluid through the system.

Thus, in one embodiment, operation of pumping mechanism 127 iscontrolled by the microprocessor using the desired set point for flowthrough the drip chamber and data regarding a measured flow rate offluid through the drip chamber. For example, the microprocessor executesa feedback loop which compares the desired flow rate with the measuredflow rate, and adjusts the pumping mechanism to correct any deviationsbetween desired and measured flow rates.

FIGS. 4A through 4C are schematic representation of embodiments foroptical system 120. The embodiments shown in FIGS. 4A through 4C formreal, conjugate images, for example, of drop 124 on a focal plane arrayformed by sensor 126. FIGS. 4A and 4B use refractive optics, such assingle lens 148 or combinations 150 of lenses, respectively. FIG. 4Cshows refractive optics, such as combination 150 of lenses, andreflective optics, such as fold mirror 152. Lens 148, combination 150,and mirror 152 can be any lens, combination of lenses, or mirror knownin the art. Combination 150 may include different lenses in FIGS. 4B and4C.

Returning to FIG. 2, in one embodiment, optical sensor 126 is a focalplane array formed by any means known in the art, including, but notlimited to a charge coupled device (CCD), a CMOS detector, or a hybridimaging array such as InGaAs bonded to a CMOS readout integratedcircuit. System 120 includes optics, such as lens 148, focused on thelocation of drop 124. It should be understood that other optics can beused in system 120. In one embodiment, chamber 106 is substantiallyoptically clear and system 118 directs light though the walls of thechamber to the optical system, for example, sensor 126. The light canprovide back or side illumination of the drop. In one embodiment, system102 is configured such that drop 124 and the focal plane array areoptical conjugates and the focal plane array records an actual image ofthe drop. The imaging system captures drop images at a rate sufficientto observe the growth and detachment of a single drop.

In one embodiment, pump 100 satisfies two key metrics with respect toimaging drop 124. First, the frame rate (images per second) issufficient to capture a sequence of images as the drop grows in size anddetaches. Second, the exposure time (the amount of time the light iscollected on the sensor for each specific image) is short enough tofreeze the motion of the drop. Pump 100 generates images with clear edgedefinition, sufficient magnification (in terms of number of pixelsacross the drop), and a minimum number of artifacts such as glare.

In one embodiment, imaging system 102 and the microprocessor produce anaccurate image of the drop that is then analyzed as described infra todetermine the volume of the drop. Since the fluid drop has a uniformdensity, and any bubbles (occlusions) or entrainments are sufficientlysmall to be negligible, in one embodiment, only the outer surface of thedrop is measured to calculate the volume of the drop. The precedingmeasurement is accomplished by imaging the drop with sufficient spatialresolution to accurately measure the boundary surface. A numericintegral over this boundary then provides the droplet volume.

FIGS. 5A through 5C illustrate imaging processing definitions. In oneembodiment, a reference/alignment frame and an image scale (pixels permm) are established by locating end point 114 of the drip tube orifice,as shown in FIG. 5A. The end point has a known size and hence providesscale calibration. The end point also represents the top boundary of thedrop, which is used in volume calculations described infra. In oneembodiment, apex 154 of the drop (a point furthest from thefixed/reference point) is identified and used in the determination ofthe volume of the drop. For example, the optical system, for example,sensor 126, receives the light transmitted into or through the drip tubeand transmitting, to the microprocessor, data regarding the receivedlight. In one embodiment, the microprocessor is for determining, usingthe data, a boundary of end point 114 and using the boundary of endpoint 114 as a reference point for determining a volume, shape, orlocation of the drop, as further described infra.

In one embodiment, as further described infra, the direction of gravity(gravity vector 156) with respect to drop 124 is determined. A referencepoint, for example, the boundary of end point 114, and the gravityvector are used to establish a reference frame for the image processing.

In one embodiment, volume of drop 124 is calculated by using themicroprocessor to receive data 129 and generate an image of the dropfrom the data. The microprocessor locates an outer edge of the drop inthe image to define boundary 157 of the drop. The microprocessorintegrates an area enclosed by the boundary and calculates a volume ofrevolution for the drop with respect to axis 159 for the drop thatintersects the end of the drip tube, assuming symmetry of the drop withrespect to the axis.

The above calculation of the volume of drip 124 can be calculated usingat least two broad approaches. The first approach, termed BoundaryConstrained Volume and shown in FIG. 5B, uses the outer location of thedrop image to calculate the total volume. Each horizontal row 158 ofpixel data from the image has associated with it an outer left and rightboundary. The area between these boundaries is treated as the twodimensional projection of a circular disk volume (the symmetric volumeof rotation of the area). The drop image is integrated from end point114 to the apex by summing the volume of each row. Boundary ConstrainedVolume obtains maximum resolution for each row of data.

The second approach is termed Fit Constrained Volume and is shown inFIG. 5C. That is, the volume of drop 124 is determined by fitting aparametric function to the boundary image of the drop and integratingthe parametric function, again, assuming rotational symmetry. There area number of possible fitting algorithms, as discussed below, but theresult of any fit is a set of parameters to the assumed function thatrepresents entire boundary 157. Fit Constrained Volume smoothes out rowdetail.

In one embodiment, the microprocessor creates a plurality of temporallysuccessive images of the drop from data 129 and calculates a respectivevolume for the drop in each successive image or calculates respectivetime periods between detachment of successive drops from the end of thedrip tube. By temporally successive images, we mean a series of imagestaken over a time period in chronological order. The microprocessorcalculates a rate of increase for the volume of the drop using therespective volumes or the respective time periods. As noted above, flowout of the drip tube is substantially equal to the increase in thevolume of the drop; therefore, the time periods between drops detachingfrom the end of the drip tube can be correlated to the volume increasesof the successive drops. For example, in one embodiment, themicroprocessor calculates a respective volume for the drop in eachsuccessive image, for example, using operations described infra andsupra; calculates changes in the respective volumes; and calculates aflow rate of fluid to the output tube based on the changes in therespective volumes. In one embodiment, the microprocessor controlsmechanism 127 to match the calculated flow rate with a desired flowrate, for example, stored in the microprocessor.

In one embodiment, the microprocessor is for generating a free flowalarm or an out of bound condition alarm when the rate of increase forthe volume of the drops exceeds a predetermined value, for example,stored in the microprocessor. In one embodiment, the microprocessor isfor operating mechanism 127 to shut off flow to the output tube when thefree flow alarm or the out of bound condition alarm is generated. In oneembodiment the microprocessor generates a downstream occlusion alarmwhen the rate of increase of the volume of the drop is less than apredetermined value. In one embodiment, the microprocessor determinesthat a drop is absent from the end of the drip tube for a specifiedperiod of time and generates an empty bag alarm or an air-in-line alarm.

In one embodiment, the pump includes processor 163 used to operatemechanism 127 to shut off flow to the output tube when the free flowalarm or the out of bound condition alarm is generated. That is, as asafety and redundancy factor, a second microprocessor is used in thepump.

The drop is initially hanging from a fixed point in the drip chamber,for example, end 114. In one embodiment, the microprocessor is foridentifying when the drop detaches from the fixed point in the dripchamber as a means of determining when the drop has reached maximumvolume. The microprocessor makes the preceding identification bycreating a plurality of temporally successive images of the drop andanalyzing these images. By temporally successive images, we mean aseries of images taken over a time period in chronological order.

In one embodiment, the microprocessor identifies, in each successiveimage, a respective point in the boundary, for example, apex 154, anddetermines a distance of each respective point from end 114. Themicroprocessor then identifies two successive images of the drop inwhich the distance, noted above, in the second image in the successionis less than the distance in the first image in the succession. Thisdecrease of the distance indicates that the drop detached from the fixedpoint in the interval between the first and second images, which furtherindicates that the drop reached a maximum size in the first image. Themicroprocessor calculates the volume of the drop using the first image.

FIG. 6 illustrates image 160 of drop 124 including circle 162 at leastpartly included within outer boundary 164 of the drop. FIG. 6illustrates a specific example of the Fit Constrained Volume approach.In one embodiment, the microprocessor identifies respective circles 162within each temporally successive image. The circles are partiallydefined by a respective outer boundaries 164 of the temporallysuccessive images. The microprocessor identifies a respective location,with respect to the fixed point in the drip chamber, for each respectivecircle and calculates a volume of the drop from the data and using therespective circles.

In one embodiment, identifying the respective location for said eachrespective circle includes identifying the image corresponding to thelargest size of the drop, for example, the last image before the dropdetaches from the end point of the drip tube. For example, themicroprocessor identifies a respective point on each respective circleat a furthest distance from the fixed point in the drip chamber, forexample, end point 114. The microprocessor then determines which of therespective points is furthest from the fixed point and identifies animage including the respective point furthest from the fixed point. Thatis, the microprocessor identifies the largest drop by identifying thedrop having the largest circle. In one embodiment, the largest drop isidentified by determining a first image in which the distance of theapex from the fixed point decreases with respect to the distance of theapex from the fixed point for a second image immediately preceding thefirst image. This decrease indicates that the drop detached from thefixed point in the interval between the first and second images, whichfurther indicates that the drop reached a maximum size in the firstimage. The microprocessor calculates the volume of the drop using theimage including the respective point furthest from the fixed point.

In one embodiment, the microprocessor identifies the respective outerboundaries for each of the temporal images such that each outer boundaryincludes a respective edge of the drop furthest from the fixed point inthe drip chamber and the respective circle includes the respective edge.That is, the microprocessor aligns the circles described supra with theactual edges of the drops such that the points of the circles furthestfrom the fixed point, for example, end 114, are part of the edge of thedrop. In one embodiment, the microprocessor identifies respectivecircular arcs corresponding to the respective edges and including therespective circular arcs in the respective circles.

In one embodiment, identifying the image corresponding to the largestsize of the drop, for example, the last image before the drop detachesfrom the end point of the drip tube, includes using the center points ofthe circles. For example, the microprocessor calculates respectivecenter points 166 for the circles and calculates the positions of thecenter points with respect to the fixed point, for example, end point114. The microprocessor then determines which of the center points isfurthest from the fixed point and identifies an image including thecenter point furthest from the fixed point. That is, the microprocessoridentifies the largest drop by identifying the drop having the largestcircle. The microprocessor calculates the volume of the drop using theimage including the center point furthest from the fixed point.

FIG. 7 is a flow chart illustrating operation of pump 100 with anoptical imaging system. FIG. 7 illustrates an example algorithm usableby pump 100. It should be understood that other algorithms are usable bythe pump. The image of drop 124 is filtered and thresholded to create abinary image. Filter operations can include median filtering (to removeisolated glare), background and image uniformity correction (to removenoise sources due to dark noise, read noise, pixel non-uniformity, andillumination non-uniformity), and edge definition (using techniques suchas convolution or unsharp masking). The resulting images are thresholdedto yield binary images. A binary image consists of values that areeither black or white, with no intermediate gray scale values. Theimages are also processed (in parallel with the above operations) tofind the reference location, for example, end point 114, usingtechniques such as feature detection, pattern matching, or transformtechniques such as the Radon transform. The end point location is usedto form an image mask. A mask isolates a region of an image for furtherprocessing. Use of a mask increases computational speed, as well aseliminates artifact information from being further processed.

In one embodiment, the binarized, masked images are then processedrow-by-row to find the extreme right- and left-boundaries. Thisboundary-constrained fit is one estimate of the drop edge shape. In oneembodiment, the images are also processed using a fit-constrainedalgorithm. Such an algorithm applies constraints based on assumptionsabout the drop shape as discussed supra and infra. The constraints areused in a non-linear least squares optimization scheme to minimize theerror between the parameterized constraint function(s) and the set ofbinarized edge images.

The two different edge approximations are provided to an Edge Estimatoralgorithm that compares fit-constrained images to boundary-constrainedimages. In the simplest instantiation, the images are comparedrow-by-row. The boundary-constrained images are considered to be the“correct” result unless they deviates from the fit-constrained images bymore than a certain parameter (this parameter is adjusted duringcalibration). If the deviation is too large, the value from thefit-constrained image is used to replace that of theboundary-constrained image for that row. The above is intended toillustrate the concept behind the estimator. In actual use, moresophisticated algorithms are used to simultaneously optimize thedifference between the two initial estimates. An example of such analgorithm is a Kalman filter, but other algorithms familiar to thoseskilled in the art may also be utilized.

The output from the Edge Estimator also provides the location of theapex of the drop, which is for example, used to calculate thetime-dependent gravity vector. This operation requires access to priorestimates of the apex value (to calculate the change), and hence anumber of prior values are stored in a buffer. The gravity vector isrequired for some of the parametric fit functions that are used in thefit-constrained edge estimation algorithms. Hence, the gravity vector isused in a feedback loop for the edge fit algorithms.

FIGS. 8A and 8B are schematic details for pump 100 implementing anoperation for determining gravity vector 156. In one embodiment, system118 illuminates end point 114 and drop 124 and the optical system, forexample, sensor 126, receives light emanating from the end point andlight emanating from the drop and transmits data 129 regarding thereceived light. The microprocessor generates, using the data, respectiveimages of the drop and the end of the drip tube and locates an apex ofthe drop, the apex being a portion of the drop at a furthest distancefrom the end of the drip tube. The microprocessor determines, using thelocation of the apex, an orientation of the drop with respect to the endof the drip tube and calculates, using the orientation of the drop withrespect to the end of the drip tube, an orientation of the drip chamber.In one embodiment, the microprocessor compares the orientation of thedrip chamber to a set point, for example, a certain orientation withrespect to plumb stored in the microprocessor, and generates an out ofbound condition alarm when the orientation equals the set point orvaries from the set point by a specified amount. For example, if thedrip chamber is too far out of plumb, operation of pump 100 may becompromised and the alarm is generated.

For example, in FIG. 8A line 168 for the actual orientation of the dropand axis 170 for the drip chamber are co-linear, Since the drop mustnecessarily align with the forces of gravity (is plumb), the dripchamber is in a plumb orientation in FIG. 8A. Also, line 168 is alignedwith gravity vector 156. In FIG. 8B, lines 168 and 170 are not co-linearand the drip chamber is not plumb. Thus, in one embodiment, themicroprocessor generates lines 168 and 170 and compares the respectivelocations or orientation of the lines. That is, the microprocessorcalculates the orientation of the drip chamber with respect to thegravity vector. In one embodiment, when data 129 is used to generaterespective images over a period of time (temporally sequential images),the gravity vector is determined by measuring in the images of the endof the drip tube and the drop, the location of the apex of the pendantdrop as it grows over time and tracking the time-dependent directionalchange of the apexes over a series of these measurements. In oneembodiment, the boundary of end 114 is calculated as described supra andthe boundary is used as reference plane for calculating the orientationof the drop and/or the drip chamber.

In one embodiment, the illumination system controls illuminationproperties of the light illuminating the end of the drip tube and thedrop and the microprocessor: identifies respective boundaries of the endof the drip tube and the drop from the respective images; fits aparametric function to the respective boundaries; and integrating theparametric function to obtain a volume of the drop, for example, asdescribed above.

In one embodiment, the end point location, gravity vector, and optimaledge estimate are input to a volume calculation routine that integratesthe edge image using the “circular disk” assumption discussed above. Thelocation of the end of the drip tube is used to determine the upperlimit of integration, while the gravity vector is used to determine thedirection of the horizontal (at right angles to the gravity vector).These end and gravity data values are provided along with the volume asoutput from the algorithm In one embodiment, the algorithm also passesout the parameters of the edge fit, as well as statistical data such asfit variances. In one embodiment, the preceding information is used inthe digital signal processing chain discussed below.

A number of methods can be used to fit a constraint to the measuredimage. In one embodiment, a “pendant drop” approach, involves solvingthe Laplace-Young equation (LYE) for surface tension. A drop hangingfrom a contact point (the end point) has a shape that is controlled bythe balance of surface tension (related to viscosity) and gravity. Theassumption is only strictly valid when the drop is in equilibrium;oscillations (due to vibration or pressure fluctuations) will distortthe drop shape from the Laplace-Young prediction. However, smalloscillations will not cause the fit to fail; in fact, the deviation froma fit is itself a good indicator of the presence of such oscillations.

In one embodiment, a Circular Hough Transform (CHT) is used on the imageto identify the component of the image that represents the curved bottomof the drop. While not strictly a “fit”, the CHT provides a parametricrepresentation of the drop that is characterized by the value and originof the radius of a circle. The CHT algorithm is representative of aconstraint that is determined or applied in a mathematical transformspace of the image. Other widely-used transforms, familiar to thoseskilled in the art, are the Fourier and wavelet transforms, as well asthe Radon transform.

The parametric fitting procedures described above apply strongconstraints on the possible location of the edge of the drop. Along withthe assumption of continuity (a fluid edge cannot deviate from itsneighbors over sufficiently short distances), and the requirement thatthe drop edge terminate at the drip tube orifice, the procedures areused to augment and correct the boundary-constrained image, as discussedabove. Other fitting procedures work similarly to those discussedherein.

FIGS. 9A and 9B are schematic details of pump 100 using light injection.Drip tube 110, drip chamber 106, tube 108, drop 124, imaging system 120,and sensor 126 are as described for FIG. 2. Illumination system 118includes illumination source 172 for transmitting, or injecting, light174 into the drip tube. The light reflects off a plurality of portionsof internally facing surface 176 of the drip tube and the reflectedlight is transmitted through the end point 114 of the drip tube intointerior 177 of drop 124 such that the interior is uniformlyilluminated. The optical system receives light 178 transmitted from theinterior of the drop and transmits, to the computer processor, dataregarding the received light. The data regarding the received light canbe operated upon using any of the operations noted supra. For example,in one embodiment, the illumination system is for controllingillumination properties of the light transmitted to the drop, and theoptical system is for receiving light from the drop. The microprocessoris for: generating an image from the data, the image including aboundary of the drop; fitting a parametric function to the boundary ofthe drop; and integrating the parametric function to obtain a volume ofthe drop.

Thus, light 174 is formed into a beam, which is injected into thetransparent drip tube so as to undergo significant internal reflection(i.e., equal to or greater than the so-called “critical angle”). Thecylindrical bore of the tube causes the internal reflections to divergeinside the tube (filling the bore of the tube), while imperfections inthe tube surface introduce light scattering. The result is that the dropis illuminated internally. Under these conditions the imaging optics insystem 120 receive only light that is scattered from the drop surface(there is no direct ray path for the light to reach the lens). Inaddition to a high contrast edge image, this approach enables the use ofa very compact illumination element.

FIG. 10A is a schematic detail of pump 100 with a meniscus detectionarrangement. Drip tube 110, drip chamber 106, tube 108, and fluid 146are as described for FIG. 2. Imaging system 102 includes light source,for example, a laser, for transmitting light 182 at an acute angle withrespect to longitudinal axis 184 for the drip chamber, into the dripchamber such that the light reflects, at the acute angle, off a surface186 of fluid pooled within the drip chamber. System 102 also includessensor, or position sensitive detector, 188 for receiving reflectedlight 182 and transmitting, to the computer processor, data regardingthe received light. The microprocessor is for calculating a position ofsurface 186 using the data regarding the received light.

The location on sensor 188 receiving light 182 depends on the locationof surface 186. Levels 190A and 190B show two possible levels for fluid146 and hence, two possible locations for surface 186. As seen in FIG.10B, light 182A and 182B reflecting from levels 190A and 190B,respectively, strike different portions of sensor 188. Themicroprocessor uses the difference between the locations on sensor 188to determine the level of fluid 146, that is, the meniscus, in the dripchamber. Sensor 188 can be any positional sensitive detector known inthe art, for example, a segmented sensor or a lateral sensor. In oneembodiment, the microprocessor generates an empty bag alarm or anair-in-line alarm for an instance in which the light transmitted fromlight source 188 is not received by the optical system, for example, thedrip chamber is empty or level 186 is so low that light 182 does notstrike fluid 146.

A segmented positional sensitive detector includes multiple activeareas, for example, four active areas, or quadrants, separated by asmall gap or dead region. When a symmetrical light spot is equallyincident on all of the quadrant, the device generates four equalcurrents and the spot is said to be located on the device's electricalcenter. As the spot translates across the active area, the currentoutput for each segment can be used to calculate the position of thespot. A lateral positional sensitive detector includes a single activeelement in which the photodiode surface resistance is used to determineposition. Accurate position information is obtained independent of thelight spot intensity profile, symmetry or size. The device response isuniform across the detector aperture, with no dead space.

FIG. 10B is a schematic detail of pump 100 with a meniscus detectionarrangement. In one embodiment, imaging system 102 includes mirror 192on the opposite side of the drip tube to reflect light 182 back throughthe drip tube and beam splitter 194 to direct the reflected light tosensor 188. This configuration enables placement of all the electronicsfor the optical components on the same side of the tube.

The following provides further detail regarding meniscus levelmeasurement. The drip chamber remains partially filled with fluid at alltimes during operation. The air trapped in the drip chamber is inpressure equilibrium with the fluid above and below it. The differencein pressure across the air gap drives fluid out of the bottom of thedrip chamber and through downstream tubing 108. Fluid enters and leavesthe drip tube chamber continuously as the drop grows in volume, andhence the meniscus level of the fluid remains nearly constant. However,changes in the meniscus level can occur for several reasons: transientchanges may occur when a drop detaches and falls into the fluid below;or fluctuations may occur due to pressure oscillations in the fluid (dueto pump vibration, motion of the tubing set, or motion of the patient).These transient changes will fluctuate around a mean meniscus value, andhence do not indicate changes in flow rate over times long compared tothe characteristic fluctuation times.

Variations that change the mean meniscus level over longer times mayoccur due to changes in the external pressure environment (e.g., in atraveling vehicle or aircraft), changes in backpressure arising frommedical issues with the patient, or due to occlusions or othermalfunctions in the pumping process. These long-term meniscus levelchanges represent a concomitant change in the overall flow rate, and maybe used to provide a refinement to the flow measurements describedsupra. Hence, it may be desired to monitor the level of the meniscusduring the infusion, and to use the information derived therein as anindicator of operational problems with the infusion system, or as anadjunct to the primary optical flow measurement.

The method described above for measuring the level of fluid 146 uses thereflection of a light beam from the top surface of the fluid in the dripchamber. The axis of the reflected beam is shifted (deflected) laterallyas the fluid level changes, for example, as shown by light 182A and182B. The amount of deflection depends only on the fluid level change,and on the incident angle of the beam. Although a laser light source isshown in the figure, the technique is compatible with any light beam.Further, although the beam is shown freely propagating, the system mayalso incorporate lens elements to control the beam.

In one embodiment (not shown), sensor 126 (the imaging focal planearray) is used both for imaging drop 124 and measuring the meniscus offluid 146 via beam splitters and other simple optics. Sensor 126 can beshared in at least two ways: a portion of the sensor that is not usedfor pendant drop imaging can simultaneously record the deflected beam;or illumination system 118 for pendant drop imaging and meniscus levelmeasurement can be alternated in time, such that the sensor alternatelyrecords the drop image and the deflected beam image. For example, pump100 can combine the imaging systems 102 shown in FIGS. 2 and 10A/10B orshown in FIGS. 2 and 9A.

Thus, in one embodiment, system 102 includes a first light source, suchas light source 172 for transmitting light into the drip tube such thatthe light reflects off an internally facing surface of the drip tube,and the reflected light is transmitted through the end of the drip tubeinto an interior of a drop of the IV fluid hanging from the first end ofthe drip tube. System 102 also includes a second light source, such aslight source 188, transmitting light, at an acute angle with respect toa longitudinal axis for the drip chamber, into the drip chamber suchthat the light reflects, at the acute angle, off a surface for IV fluiddisposed within the drip chamber. Optical sensor 126 is for: receivingthe reflected light transmitted from the interior of the drop; receivingthe reflected light from the second light source; and transmitting, tothe computer processor, data regarding the received light from the firstand second light sources. The microprocessor is for calculating a volumeof the drop using the data regarding the light received from the firstlight source, and calculating a position of the surface of the using thedata regarding the light received from the second light source, asdescribed supra.

FIG. 11 is a schematic block representation of pump assemblies 200A and200B with respective optical imaging system in a primary and secondaryconfiguration. The assemblies include the components for pump 100described supra, with the exception of the processor and control panel.In general, the description above regarding the operation of pump 100 isapplicable to the operation of assemblies 200A and 200B. Assembly 200Ais connected to primary fluid source 112A. Pump 200B is connected toprimary fluid source 112B. Sources 112A and 112B are arranged in aprimary/secondary infusion configuration. For example, a primarymedication in source 112A is administrated in coordination with asecondary medication in source 112B. As is known in the art, in aprimary/secondary configuration, the medication in the secondary sourceis infused before the medication in the primary source. Tubings 108A and108B from pump mechanisms 127A and 127B, respectively, are connected tocommon tubing 202.

In one embodiment, a single processor and control panel, for example,processor 104 and panel 144 are used for assemblies 200A and 200B. Theprocessor operates assembly 200B according to appropriate protocolsuntil the regime for the fluid in source 112B is completed. Then, theprocessor automatically deactivates assembly 200B as required and beginsthe infusion of the fluid in source 112A. In one embodiment (not shown),each assembly has a separate processor and control panel or eachassembly has a separate processor and a common control panel.

FIG. 12 is a top-level block diagram illustrating operation of pump 100with an optical imaging system. In one embodiment, the volumemeasurement, and fit metrics if applicable, described above are fed intoa digital signal processing algorithm that calculates the flow rate andprovides feedback to the pump control system. Plant 210 includes source112, the drip chamber, the drip tube, and pump mechanism 127. Themicroprocessor outputs the Volume and Fit Metrics 212, which arefiltered by digital filter 214 in a portion of the microprocessor toprovide measured flow rate 216. The measured flow rate is compared withthe desired flow rate, for example, input into the microprocessor viapanel 144, closing the feedback loop for pump 100.

FIG. 13 is a block diagram illustrating example signal processing andfeedback control for pump 100 with an optical imaging system. Mechanism127 includes drive 218 and motor 220. Imaging data from system 102 isprocessed by image processing block 222 to generate a Measured DropVolume, and the results are input to filter block 224. The output of thefilter block is the Measured Flow Rate. The Measured Flow Rate iscompared to the Desired Flow Rate by comparator 226, providing the ErrorFlow Rate (error estimate). The Error Flow Rate feeds into a stagedseries of PID (Proportional, Integral, Derivative) control algorithms228. Each PID block operates on a successively faster time scale. Block228A controls the flow rate, block 228B controls the pump motor speed,and block 228C controls the pump motor current. The speed controlincorporates feedback from motor position encoder 230. The currentcontrol incorporates feedback from a motor current sensor in motor 220.

FIG. 14 is a block diagram illustrating example digital filtering inpump 100 with an optical imaging system. Filter 232 can be any filterknown in the art, for example, the general class of FIR/IIR filtersknown to those skilled in the art. A simple example is an FIR filterthat implements a time average over a number of samples.

FIG. 15 is a schematic representation of example spatial filtering inpump 100 with an optical imaging system. The goal of high resolution andedge definition for images of drop 124 are attained by illuminationtechniques, optical techniques, or both, for example, as describedsupra. In one embodiment, spatial filtering techniques are used in theoptics for system 120. For example, mask 240 at the back focal plane ofimaging system 102 modifies (via optical Fourier transform) the imagegenerated by the optical system, for example, sensor 126. A DC blockfilter is shown in FIG. 15. This filter blocks the central cone of thetransmitted light and enhances edge images (associated with scatteredlight).

In one embodiment, the sensitivity of sensor 126 is matched to theillumination spectrum of the light source in system 118. In oneembodiment, sensor 126 is a low-cost visible light sensor (400-1000 nmwavelength) and source 122 generates light that is outside the range ofhuman visual perception (i.e., 800-1000 nm). In this case the operatorwill not be distracted by the bright illumination source.

It should be understood that pump 100 can be any pump mechanism or pumpapplication known in the art and is not limited to only IV infusion pumpapplications. In the case of a gravity-fed system, the pumping mechanismcan be replaced by a valve or flow restrictor, and still be compatiblewith the configurations and operations described supra.

Thus, it is seen that the objects of the invention are efficientlyobtained, although changes and modifications to the invention should bereadily apparent to those having ordinary skill in the art, withoutdeparting from the spirit or scope of the invention as claimed. Althoughthe invention is described by reference to a specific preferredembodiment, it is clear that variations can be made without departingfrom the scope or spirit of the invention as claimed.

What is claimed:
 1. A method of operating a flow meter, comprising:using a pattern in association with a drip chamber, wherein the patternincludes pattern information; generating one or more images of a drop offluid and drip chamber, wherein the image is generated using datareceived from an optical system having a sensor; comparing the one ormore images of the drop of fluid with the pattern information; andcalculating at least one fluid property based on the one or more imagesof the drop of fluid and the pattern information.
 2. The method of claim1, wherein the at least one fluid property is the volume of the drop offluid.
 3. The method of claim 1, wherein the calculation of the at leastone fluid property is used to determine whether a free flow conditionexists.
 4. The method of claim 1, wherein the pattern is configured suchthat the pattern is viewable on the surface of the fluid.
 5. The methodof claim 4, wherein the pattern is a stripe pattern.
 6. The method ofclaim 5, wherein the stripe pattern includes an array of lines.
 7. Themethod of claim 6, wherein the array of lines are parallel stripes.
 8. Amethod of controlling a flow meter, the method comprising: generatingone or more images of a drop of fluid and a drip chamber, wherein theimage is generated using data received from an optical system having asensor; calculating a flow rate of fluid, using one or moremicroprocessors, through the drip chamber based on data received fromthe sensor; and controlling a mechanism, using the one or moremicroprocessors, to achieve a target flow rate, the mechanism comprisinga flexible tube section, a pump, and one or more flow restrictors. 9.The method of claim 8, wherein the mechanism is adjusted to correct anydeviations between the desired and measured flow rates.
 10. The methodof claim 8, wherein the one or more flow restrictors are actuators.